Lighting has many components to it. The three that I would like to discuss are the components that are commonly used to evaluate the quality of the light we provide our fish and our aquatic plants.

The first component is what is referred to as the "K". This is what is referred to when we are talking about the focus of a particular bulb. For planted aquariums, you will want to have your focus as close to 5600K as possible. This focus seems to be the best for your plants. If you look at a graph of the light showing many points along the full spectrum of light you will see many spikes in the 5600 range on a graph.

The lighting industry is still trying to emulate the "full spectrum daylight". This elusive quality is what most bulb manufacturers are working towards, none have achieved this yet. They are getting closer.

The next component you most often hear of is full spectrum. The spectrum of lighting has many points along the graph, how often the point comes to the top in a graphical analysis is how close they get to the full spectrum. To have one tube hit all of the points along this long graph is impossible in todays world. Most people use more than one bulb in combination to achieve a greater spread on these range. Full spectrum includes all parts of light from infrared to ultraviolet. Please keep in mind that the human eye does not see all of these points of light.

The last and one of the most important components of quality of light in my eye is what is called the CRI. The Color Rendition Index is the component that allows us to evaluate how close the light we are using is coming to the full spectrum of natural sunlight. I like to think of it as True Color. Is this really what red looks like or is this just a deep orange red color, that I am looking at? True color rendition is still elusive at this time but this index lets us know how close we have come.

In summary, one should make sure the K of the bulb they use is close to the 5600 mark to mostly benefit your plants with the part of the spectrum they need. Full spectrum is the most natural light you can get. And CRI is what evaluates if it looks like True Color to the human eye.